package com.example.bitmapandcachedemo.imageloader;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.Log;

import java.io.FileDescriptor;

/**
 * Created by tangjiangxu on 11/8/17.
 */

public class ImageResizer {
    private static final String TAG = "ImageResizer";

    public Bitmap decodeSampledBitmapFromResource(Resources res, int resId, int reqWidth, int reqHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;

        BitmapFactory.decodeResource(res, resId, options);

        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
        options.inJustDecodeBounds = false;

        return BitmapFactory.decodeResource(res, resId, options);
    }

    public Bitmap decodeSampledBitmapFromFileDescriptor(FileDescriptor fd, int reqWidth, int reqHeight) {
        BitmapFactory.Options options = new BitmapFactory.Options();
        options.inJustDecodeBounds = true;

        BitmapFactory.decodeFileDescriptor(fd, null, options);

        options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);
        options.inJustDecodeBounds = false;

        return BitmapFactory.decodeFileDescriptor(fd, null, options);
    }

    private static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        if (reqHeight <= 0 || reqWidth <= 0) {
            return 1;
        }
        final int height = options.outHeight;
        final int width = options.outWidth;
        int inSampleSize = 1;
        if (height > reqHeight || width > reqWidth) {
            final int halfHeight = height / 2;
            final int halfWidth = width / 2;
            //calculate the largest inSampleSize value that is a power of 2 and keeps both
            //height and width larger than the requested height and width
            while ((halfHeight / inSampleSize) >= reqHeight && (halfWidth / inSampleSize) >= reqWidth) {
                inSampleSize *= 2;
            }
        }
        Log.d(TAG, "calculateInSampleSize: inSampleSize:" + inSampleSize);
        return inSampleSize;
    }
}
